An Australian drugs trial lasting more than three months and costing taxpayers over A$1 million ($947,000) has been aborted after a number of jurors were found to have spent up to half the time playing Sudoku puzzles.

Sydney District Court Judge Peter Zahra cancelled the trial of two men on drugs conspiracy charges after the jury foreperson admitted that four to five jurors had been playing the addictive number sequence game, local media reported. The judge was alerted after some of the jurors were observed writing their notes vertically, rather than horizontally. The game involves completing a grid of numbers in the correct sequence.

One juror said the game helped them to pay more attention by keeping their mind busy.

"Some of the evidence is rather drawn out and I find it difficult to maintain my attention the whole time," the juror was quoted saying by the Australian Associated Press.

A new trial is expected to begin in a few weeks once a new jury has been called.